Following up on last week's post about Yukon River freeze-up at Dawson City (Yukon Territory), it's worth looking at whether excessive warm season precipitation may have been a factor in preventing a complete freeze-up in some recent years. To recap, the Yukon failed to freeze over properly at Dawson in the winters of 2016-17 though 2018-19, and then again last winter; but freeze-up did succeed in 2019-20 through 2022-23, and again this winter.
Here are the May-September precipitation estimates from ERA5 for the months prior to the "no freeze" winters:
There's no evidence here that the southern half of the Yukon Territory (much of which is in the Yukon drainage) was consistently wetter than normal in these years, and in fact the summer of 2023 was somewhat dry.
As for recent "normal freeze" years, 2019 was dry, but others years tended to be more on the wet side; and this summer wasn't particularly unusual in either direction.
How about water levels at Dawson? Here are the September mean water levels in the no-freeze years, for the Yukon River (left) and the tributary Klondike River (right), which meets the Yukon immediately upstream of downtown Dawson:
2016 2.02m 1.36m
2017 1.56m 1.23m
2018 1.85m 1.10m
2023 1.60m 1.30m
And the normal freeze-up years:
2019 1.03m 0.85m
2020 2.65m 1.39m
2021 2.30m 1.28m
2022 2.16m 1.65m
2024 2.12m 1.50m
With the exception of 2019, the normal freeze-up years all had higher Yukon River levels in September than the no-freeze years. The tendency is the same for the Klondike River, with 2022 and 2024 both having higher levels than the no-freeze 2023.
I think we can therefore dispense with the idea that the freeze-up failures occurred because of higher flows - if anything, the reverse seems to be more likely - but I won't indulge in any more speculation now. Previous posts and discussions in the blog comments can be accessed by searching the blog archives for "Dawson".
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